Corrosion resistant sealing member

ABSTRACT

A corrosion-resistant sealing member comprising: a relatively rigid cylindrical member, made from a corrosion-resistant material deformable under applied pressure, with a passage connecting its ends, a flange at one end extending outward from its outer periphery, and a groove at the other end extending inward from its outer periphery in a manner such as to provide a thin flexible wall between the groove and the adjacent end of the cylindrical member; a first gasket disposed within the groove; and a second gasket disposed about the cylindrical member abutting the flange, both gaskets being made from materials that are resilient over the range of temperature variation to which they are subjected.

United States Patent [56] References Cited UNITED STATES PATENTS2,868,575 1/l959 Hawxhurst 277/228 2,951,721 9/1960 Asp 277/DIG. 6

Primary Examiner-Robert J. Smith Attorneywilkin E. Thomas, Jr.

ABSTRACT: A corrosion-resistant sealing member comprising: a relativelyrigid cylindrical member, made from a corro sion-resistant materialdeformable under applied pressure, with a passage connecting its ends, aflange at one end extending outward from its outer periphery, and agroove at the other end extending inward from its outer periphery in amanner such as to provide a thin flexible wall between the groove andthe adjacent end of the cylindrical member; a first gasket disposedwithin the groove; and a second gasket disposed about the cylindricalmember abutting the flange, both gaskets being made from materials thatare resilient over the range of temperature variation to which they aresubjected.

PATENIED our 5 I9?!- sum 2 or 2 F I G- INVENTOR LOUIS T. STAATS, JR,

AGENT CORROSION RESISTANT SEALING MEMBER BACKGROUND OF THE INVENTIONThis application relates to corrosion-resistant sealing members. Moreparticularly it relates to corrosion-resistant sealing members useful ina plastic tube heat exchanger adapted to operate on corrosive fluids.

When two conduits used to pass corrosive fluids are joined, the sealbetween them as well as the internal surface of the conduits must bemade from a material which is resistant to the corrosive fluid.Normally, this means that the seal must be made from a deformablethermoplastic rather than a resilient elastomer. Since the material fromwhich the conduits are made is usually a metal, perhaps with a plasticliner, having a coefficient of thermal expansion much less than that ofthe thermoplastic, if the corrosive fluid is subjected to largetemperature variations, then the thermoplastics will take a set at thehigh temperature under the compression due to the difference in thermalexpansion, and the set will remain when the temperature of the fluid isdecreased, causing the seal to leak. This can in part be overcome byusing a resilient gasket either completely or partially encapsulated bythe thermoplastic, but in those cases where the connection between theconduits is provided for the purpose of supporting an internal structurebetween the conduits, then the necessity for two seals, one on eitherside of the structure, and the inconvenience of assembling such acombination makes an integrated structure desirable and in many casesnecessary. One case in which this situation arises is in a plastic tubeheat exchanger where one conduit supplied the tube-side fluid, the otherconduit supplies the shell-side fluid and the structure sealed betweenthe conduits is the tube sleeve for the plastic heat exchanger tubes. Inthis case, not only must the seals between the two conduits be leaktightin relationship to the exterior of the conduits, but the seal must beleaktight as between the two conduits so that the shell-side fluid andthe tube-side fluid will not intermix.

The simple solution that has been arrived at in cases like this is toincorporate resilient regions into a rigid corrosion resistant materialthat is deformable under applied pressure, so that at highertemperatures the rigid material can expand into the region occupied bythe resilient material without compressing and taking a set. Thesimplest way to accomplish this in a structure such as the tube sleeveof. the plastic tube heat exchanger discussed above is to cut groovesinto its outer periphery at each end of the tube sleeve and to placeresilient gaskets into these grooves. While simple, this solution is notas attractive as it might at first appear, because many of thestructures designed to be inserted between such conduits are bothdifficult and expensive to manufacture. Care must be taken to insurethat accidental destruction of the sealing member will not causecomplete loss of the structure. In many cases, therefore, it isessential to have a sealing member which is not part of the structure tobe sealed between the conduits, and the problem becomes one ofconstructing a separate seal ing member which is as simple, aseffectiveand as corrosion resistant as the integral seal.

It is an object of the present invention, therefore, to provide acorrosion resistant sealing member for connecting conduits adapted topass corrosive fluids, which will withstand wide variations intemperature without sustaining a leak. It is a further object of thepresent invention to provide a corrosionresistant sealing member adaptedto connect two conduits together in a manner such as to support a thirdstructure between them, all having leaktight association over a widevariation in temperature. It is a still further object of the presentinvention to provide a corrosion-resistant sealing member adapted tosupport and to seal a structure between two conduits in leaktightarrangement over a wide variation in temperature, in which the sealingmember is not an integral part of the structure. It is a still furtherobject of the present invention to provide a corrosion-resistant sealingmember for use in forming a seal between the shell-side fluid conduitand tube-side fluid conduit of a plastic heat exchanger in a manner suchas to support the tube sleeve of a plastic heat exchanger tube betweenthe two conduits.

SUMMARY OF THE INVENTION These objects are accomplished by providing acorrosionresistant sealing member comprising: a relatively rigidsubstantially cylindrical member made from a corrosion-resistantmaterial that is deformable under applied pressure, and first and secondcircular gaskets made from materials that are resilient over the rangeof temperature variation to which they are subjected. The cylindricalmember has a passage connecting its ends, a flange at one of its endsextending outward from its outer periphery, and a groove at its otherend extending inward from its outer periphery in a manner such as toprovide a thin flexible wall between the groove and the end of themember adjacent to the groove. The first gasket is disposed within thegroove and the second gasket is disposed about the outer periphery ofthe cylindrical member abutting the flange. In a preferred embodiment,the cylindrical member is made from a thermoplastic, such asTeflonfluorocarbon resin and the gaskets are made from a material;having a hardness of between 30 and 60 durometers. The sealing membercan be adapted to both seal the tube-side and shell-side of the heatexchanger and to support the tube sleeve between them, all in leaktightrelationship. In this case, the end of the cylindrical member containingthe groove further comprises a flange, extending inward from the innerperiphery of the cylindrical member, into which the gasket containinggroove extends, to provide a surface for the tube sleeve of the heatexchanger to butt and seal against, giving the sealing member a z-shapedconfiguration. A separate split-ring retaining ring is also provided atthe other end of the seal to firmly seat the tube sleeve within theregion formed for it in the sealing member.

The operation and advantages of the present invention can best bediscussed by reference to the following figures wherein:

FIG. 1 is a cross-sectional diagram of one embodiment of the sealingmember of the present invention in situ between the tube-side conduitand shell-side conduit of a heat exchanger; and

FIG. 2 is a cross-sectional diagram of a second embodiment of thesealing member of the present invention.

DETAILED DISCUSSION OF THE FIGURE Referring to FIG. 1, the sealingmember 11, comprises a substantially cylindrical member 12 with a flange13 at one end and a groove 14 at the other end, and first and secondcircular gasket, 15 and 16 respectively. The first gasket 15 is disposedwithin groove 14 and the second gasket 16 is disposed about thecylindrical member :abutting flange 13.

The cylindrical member is made from a relatively rigid material that isdeformable under applied pressure and is unaffected by the hot corrosivefluid that flows through conduits l7 and 18. The material must berelatively rigid so that it will withstand the forces involved in thesealing, and it must also be deformable under applied pressure becausethe seal itself is formed by deformation of the material in thecylindrical member. Usually the cylindrical member is made from athermoplastic. Those thermoplastics that are particularly resistant tochemical corrosion are the fluorocarbon polymers sold under thetrademark Teflon, comprising polymers of tetrafluoroethylene orcopolymers of tetrafluoroethylene and hexafluoropropylene. Otherthermoplastics such as polyamides, polyolefins and polyacetals may besuitable under certain circumstances.

Gaskets l5 and 16 are made from materials which are resilient and retaintheir resiliency over the range of temperature to which they aresubjected. Materials with a hardness of between 30 and 60 durometers aresuitable. Much below this value, the gaskets are given to excessiveextrusion; much above it, they become too hard for the function they aremeant to perform. Rubber, fabric reinforced rubber and synthetic rubberssuch as silicone rubber or Nordel hydrocarbon rubber are examples ofmaterials that have been found to function well as the gasket material.

As illustrated, the substantially cylindrical member is a right circularcylinder. It is to be understood, however, that cylinders with crosssections of different shapes, such as square, rectangle or convoluted,are meant to be incorporated in the broad meaning of the termcylindrical as long as they serve a like function.

In the embodiment illustrated, conduit 17 is the tube-side fluid supplyline and conduit 18 is the shell of a plastic tube heat exchanger. Theplastic heat exchanger tubes 19 are bonded to themselves and to tubesleeve 20. The tube sleeve is then sealed between the two conduits asshown. One process for achieving a bond between the heat exchanger tubesand the tube sleeve is described in U.S. Pat. No. 3,315,740 issued to M.S. Withers on Apr. 25, 1967. Flange 21 is provided at the end of thecylindrical member housing the groove and the groove extends into thisflange. This flange acts as a seat for the tube sleeve and provides ameans for forming a seal between the tube-side flow line 17 and thesleeve 20. To keep the tube sleeve 20 from pulling into the shell asplit-ring retainer 22 is supplied.

1 Registered trademark of E. l. du Pont de Nemours and Co.

The shell-side conduit 18 comprises a tube 23 to which a flange 24 isattached. Usually these parts are metal, so the attachment is made by aweld. if the shell-side fluid is corrosive, the shell-side conduit maybe lined with a plastic sheath, or it may be made from a relativelyimpervious metal such as cast iron. The split-ring retainer and the heatexchanger tubes are held in place by member 11 which is sealed to theshell-side conduit by means of a retainer ring 25 adapted to mate withflange 24 of the shell-side conduit and compress gasket 16 and flange 13between them. Compression is supplied by bolts 26, and the seal is madeat the interface between flange l3 and flange 24. Gasket 16 plays nopart in the actual sealing. lts sole purpose is to provide a resilientbacking for the seal. The material from which the cylindrical member 12is made generally has a coefficient of thermal expansion much greaterthan the material from which the conduits are made. As the temperatureof the fluid flowing through the conduits increases, both the conduitsand the sealing member will expand. Without the resilient gasket, flange13 would be compacted by the force caused by the difference in expansionbetween it and the conduits and retainer ring. Aside from having a highcoefficient of thermal expansion, those corrosion resistantthermoplastics most suitable to form the seal also take a set at hightemperatures. The seal is still good at high temperatures, but when thetemperature is reduced, the thermoplastic retains its set as thematerial around it contracts, and a leak develops. The purpose of thegasket 16 is to allow the thermoplastic of the cylindrical member 11 toexpand more than the material surrounding it without being subject tosufficient compressive stress to cause a set to occur. It is for thisreason that the gaskets must be made from materials which retain theirresiliency over the range of temperature to which they are subjected.

Tube-side conduit 17 comprises a tube 27 and a flange 28 attached to it.Since the tube-side fluid is a corrosive fluid, the conduit is linedwith a corrosion-resistant liner 29, made from a material similar to thematerial from which member 12 is made. The flange 28 is designed to matewith the grooved end of member 12 and compression of the seal isprovided by bolts 30. As illustrated the series of bolts 26 and theseries of bolts 30 alternate around the periphery of both flanges 24 and28 and retainer ring 25 to provide compression at both ends of the seal.At the tube-side connector, the seal is formed between the liner 29 andthe outer wall of flange 21, and between the tube sleeve 20 and theinner wall of flange 21, with the gasket again merely providingresiliency.

Since the seal is actually formed by compression, of the material inmember 12, and since this compression must occur without substantialdeformation of member 12, the machining tolerances on member 12 arestringent. To relieve this manufacturing difficulty slots 31 and 32 havebeen cut in member 12, providing some resiliency in the relatively rigidmember itself.

Furthermore, since some compression of member 12 is bound to occur,especially at the end containing groove 14, a precaution has been takento insure that compression is possible at that end without damaging thatportion of flange 21 which does not contain gasket 15. This isaccomplished by insuring that the gasket 14 is slightly wider than thegroove into which it is placed. When the gasket is inserted into thegroove,

it does not fit all the way to the bottom of the groove, but lodgesabove the bottom of the groove, as shown, forcing the wall of the grooveat the end of member 12 to spread. Thus,

when compression first occurs, the seal is first formed at the point onthe bottom of the gasket where the gasket fully bridges the groove. Ascompression continues, full contact between the gasket and walls of thegroove, proceeds upward towards the outer periphery of member 12 leavingthe solid base of the flange substantially free from destructivecompresson.

A number of variations and modifications are possible. For example, asillustrated in FIG. 2 flange 13 at the other end of member 12 may alsocontain a groove in which gasket 16, instead of being disposed behindthe flange can be placed. in this case, the gasket should also bedesigned to spread the walls of the groove for maximum protection ofmember 12. Also gaskets l5 and 16 need not be made from the samematerial.

What is claimed is:

l. A corrosion-resistant sealing member, for connecting conduits,comprising:

a. a relatively rigid substantially cylindrical member made from acorrosion-resistant material deformable under applied pressure, saidsubstantially cylindrical member having a first flange at one endthereof extending outward from its outer periphery and adapted to matewith a first one of said conduits, a first groove at the other endthereof extending inward from its outer periphery in a manner such as toprovide a thin flexible wall between said first groove and the end ofsaid substantially cylindrical member associated therewith and adaptedto mate with a second one of said conduits, and a passage therethroughconnecting both ends of said substantially cylindrical member;

b. a first circular gasket disposed within said first groove;

and

c. a second circular gasket disposed about the outer periphery of saidsubstantially cylindrical member, abutting said first flange, said firstand second circular gaskets being made from materials that are resilientover the range of temperature variation to which they are subjected.

2. The corrosion-resistant sealing member of claim 1 wherein thematerial of said substantially cylindrical member is thermoplastic.

3. The corrosion-resistant sealing member of claim 1 wherein thematerial from which said substantially cylindrical member is madecomprises a polymer of tetrafluoroethylene.

4. The corrosion-resistant sealing member of claim 1 wherein thematerial from which said substantially cylindrical member is madecomprises a copolymer of tetrafluoroethylene and hexafluoropropylene.

5. The corrosion-resistant sealing member of claim 1 wherein thematerial from which said first and second circular gaskets are made hasa hardness of between 30 and 60 durometers.

6. The corrosion-resistant sealing member of claim 1 wherein thematerial of said substantially cylindrical member is thermoplastic, andwherein the material from which the said first and second circulargaskets are made has a hardness of between 30 and 60 durometers.

7. The corrosion-resistant sealing member of claim 1 wherein said firstflange contains a second groove extending inward from the outerperiphery thereof in a manner such as to provide a thin flexible wallbetween said second groove and the end of said substantially cylindricalmember associated therewith, and wherein said second circular gasket isdisposed within said second groove.

8. The corrosion-resistant sealing member of claim 1 wherein said firstcircular gasket has a width slightly greater than the width of saidfirst groove, whereby, in an uncompressed state, said first circulargasket extends only part of the way to the bottom of said first grooveand the wall of said first groove adjacent to the end of saidsubstantially cylindrical member is forced outward from the end of saidsubstantially cylindrical member, thereby allowing compression of saidfirst circular gasket and the formation of a seal before destructivedeformation of said substantially cylindrical member occurs.

9. The corrosionresistant sealing member of claim 1 wherein saidsubstantially cylindrical member further comprises a second flange, atthe end thereof containing said first groove, extending inward from itsinner periphery, thereby forming a z-shaped sealing member, and whereinthe bottom of said first groove extends into said second flange.

10. The corrosion-resistant sealing member of claim 9 further comprisinga separate split-ring retaining member adapted to mate with the end ofsaid substantially cylindrical member containing said first flange in amanner such as to provide a rim extending from the inner periphery ofsaid substantially cylindrical member, whereby a support groove forsupporting a structure within said corrosion resistant sealing member isformed between said second flange and the rim formed by said split-ringretaining member.

1. A corrosion-resistant sealing member, for connecting conduits,comprising: a. a relatively rigid substantially cylindrical member madefrom a corrosion-resistant material deformable under applied pressure,said substantially cylindrical member having a first flange at one endthereof extending outward from its outer periphery and adapted to matewith a first one of said conduits, a first groove at the other endthereof extending inward from its outer periphery in a manner such as toprovide a thin flexible wall between said firSt groove and the end ofsaid substantially cylindrical member associated therewith and adaptedto mate with a second one of said conduits, and a passage therethroughconnecting both ends of said substantially cylindrical member; b. afirst circular gasket disposed within said first groove; and c. a secondcircular gasket disposed about the outer periphery of said substantiallycylindrical member, abutting said first flange, said first and secondcircular gaskets being made from materials that are resilient over therange of temperature variation to which they are subjected.
 2. Thecorrosion-resistant sealing member of claim 1 wherein the material ofsaid substantially cylindrical member is thermoplastic.
 3. Thecorrosion-resistant sealing member of claim 1 wherein the material fromwhich said substantially cylindrical member is made comprises a polymerof tetrafluoroethylene.
 4. The corrosion-resistant sealing member ofclaim 1 wherein the material from which said substantially cylindricalmember is made comprises a copolymer of tetrafluoroethylene andhexafluoropropylene.
 5. The corrosion-resistant sealing member of claim1 wherein the material from which said first and second circular gasketsare made has a hardness of between 30 and 60 durometers.
 6. Thecorrosion-resistant sealing member of claim 1 wherein the material ofsaid substantially cylindrical member is thermoplastic, and wherein thematerial from which the said first and second circular gaskets are madehas a hardness of between 30 and 60 durometers.
 7. Thecorrosion-resistant sealing member of claim 1 wherein said first flangecontains a second groove extending inward from the outer peripherythereof in a manner such as to provide a thin flexible wall between saidsecond groove and the end of said substantially cylindrical memberassociated therewith, and wherein said second circular gasket isdisposed within said second groove.
 8. The corrosion-resistant sealingmember of claim 1 wherein said first circular gasket has a widthslightly greater than the width of said first groove, whereby, in anuncompressed state, said first circular gasket extends only part of theway to the bottom of said first groove and the wall of said first grooveadjacent to the end of said substantially cylindrical member is forcedoutward from the end of said substantially cylindrical member, therebyallowing compression of said first circular gasket and the formation ofa seal before destructive deformation of said substantially cylindricalmember occurs.
 9. The corrosion-resistant sealing member of claim 1wherein said substantially cylindrical member further comprises a secondflange, at the end thereof containing said first groove, extendinginward from its inner periphery, thereby forming a z-shaped sealingmember, and wherein the bottom of said first groove extends into saidsecond flange.
 10. The corrosion-resistant sealing member of claim 9further comprising a separate split-ring retaining member adapted tomate with the end of said substantially cylindrical member containingsaid first flange in a manner such as to provide a rim extending fromthe inner periphery of said substantially cylindrical member, whereby asupport groove for supporting a structure within said corrosionresistant sealing member is formed between said second flange and therim formed by said split-ring retaining member.